Intraocular lenses intended to replace the crystalline lens have been used for some time to treat patients suffering from ocular disorders such as cataracts. In a typical procedure, after extracting and removing the crystalline lens from inside the capsule through a surgical incision made in the ocular tissue, such as the cornea (sclera) or anterior capsule portion of the lens, an insertion instrument or the like is used to insert the intraocular lens into the capsule through the surgical incision while folded back onto itself. Once inserted into the capsule, the intraocular lens is deployed inside the capsule to allow it to be used with the optical part thereof, which replaces the functionality of the crystalline lens, securely positioned within the capsules by means of support portions.
Secondary cataracts are a subsequent complication sometimes encountered as a problem with intraocular lens replacements. Secondary cataracts occur when subsequent to surgery, the epithelial cells of the crystalline lens grow around to the back face of the intraocular lens, clouding the posterior capsule to the back side of the intraocular lens and causing a decline in vision.
One known technique for inhibiting secondary cataracts, disclosed for example in Patent Document 1 and Patent Document 2, involves imparting sharp edge contours to the outside peripheral edge portion of the back face of the optical part of the intraocular lens, and deploying the lens within the capsule so that the sharp edge presses against the posterior capsule, thereby preventing epithelial cells of the crystalline lens from growing around towards the lens back face. However, with this method the optical part tends to be thicker as a result of the sharp edge contours, and the surgical incision required for insertion into the capsule must be larger, posing the problem of difficulty in folding the lens during the insertion process.
In Patent Document 3 there is proposed an intraocular lens having at least one annular groove extending continuously in the circumferential direction through the outside peripheral section of the intraocular lens and formed with a cross section sufficiently large to accommodate epithelial cells on the crystalline lens, and provided on the surface of this annular groove with a microgrooved irregular face. According to this intraocular lens, through a feature combining this large annular groove with a microgrooved irregular face, epithelial cells on the crystalline lens may be captured in the annular groove in the outside peripheral section of the intraocular lens, preventing growth of epithelial cells on the crystalline lens towards the center section of the intraocular lens.
However, in order for the feature of combining a large annular groove and a microgrooved irregular face as taught in Patent Document 3 to afford effective action in trapping epithelial cells on the crystalline lens and inhibiting epithelial cell growth, the annular groove must be formed with a size enough to create an opaque section in which light is not able to be focused on the retina. Thus, the intraocular lens disclosed in Patent Document 3 has, in the outside peripheral section thereof where the annular groove is formed, an opaque section that cannot be employed as part of the effective optical part. The effective optical part of an intraocular lens is preferably as large as possible so as to ensure that sufficient light enters under conditions of limited outside diameter dimension imposed by deploying of the lens within the lens capsule, and to provide a good field of vision through overlap of the entire pupil in a reliable manner. However, because the outside peripheral section of the intraocular lens taught in Patent Document 3 is an opaque section, an adequate effective optical part is not necessarily assured, making it difficult to provide a good field of vision.
Patent Document 1: JP-A 2005-507742
Patent Document 2: WO 2004/096099
Patent Document 3: JP-A 11-505453